Drinking a lot of soda may uncork bottled-up aggression in teens, researchers have found.

Those who drank more than five cans of soft drinks per week were significantly more likely to have carried a weapon and to have been violent with peers, family, and their dates, Sara Solnick, PhD, and David Hemenway, PhD, of the University of Vermont, reported online in Injury Prevention.

"There may be a direct cause-and-effect relationship, perhaps due to the sugar or caffeine content of soft drinks," they wrote.

In their paper, Solnick and Hemenway noted that the murderer of gay rights activist Harvey Milk had his conviction reduced from homicide to voluntary manslaughter by the "Twinkie Defense," which stated that an unhealthful diet made the perpetrator act irrationally.

Some studies have in fact shown that drinking lots of sugary drinks is linked with poor mental health and diminished social abilities, they wrote, though the literature remains unclear.

So to investigate the link between soda consumption and violence, they conducted a survey of Boston public high schools. Students were asked how often they drank soda and whether they carried a weapon or engaged in violence.

A total of 1,878 kids responded to the survey — half were black, 33 percent were hispanic, 9 percent were white, and 8 percent were Asian.

Nearly 30 percent of all respondents reported drinking more than five cans of non-diet soda every week.

Solnick and Hemenway found that those who drank more than five cans of soda per week were significantly more likely to have carried a weapon than those who drank less.

They were also more likely to have been violent with peers, family members, and dates, they reported.

In multivariate analyses, drinking lots of sodas increased the probability of aggressive behavior between 9 and 15 percentage points, the researchers reported, even after controlling for factors such as gender, age, race, body mass index, typical sleep patterns, tobacco use, alcohol use, and having family dinners.

They found that the impact of drinking lots of soda on violence was similar in magnitude to the impact of using tobacco or alcohol.

However, high soda intake's influence on the probability of carrying a weapon wasn't as strong an influence as alcohol or tobacco, although it was significant, they said.

Solnick and Hemenway added that it appears to be a dose-response relationship, with violent effects increasing at greater consumption. The reason for the relationship, however, isn't clear, they wrote. It could be a direct cause-and-effect, as diet can influence behavior, and soda has a host of potentially culprit ingredients — i.e. high fructose corn syrup, aspartame, sodium benzoate, phosphoric or citric acid, and caffeine.

Still, they cautioned that there could be other factors that aren't accounted for, and the survey can't prove causality.

Other limitations include its reliance on self-reported data, having limited information about the types of sodas consumed, and having no information on students' overall diets. The findings may also not be generalizable, given that the survey population was largely black and Hispanic.